1. Field of the Invention
This invention relates generally to patterned magnetic recording media, such as disks for use in magnetic recording hard disk drives, and more particularly to a patterned medium and recording system wherein the data islands are arranged in a pattern that improves reading and writing.
2. Description of the Related Art
Magnetic recording hard disk drives with patterned magnetic recording media have been proposed to increase data density. In a patterned medium the magnetic recording layer on the disk is patterned into small isolated data islands arranged in concentric data tracks. Patterned-media disks may be longitudinal magnetic recording disks, wherein the magnetization directions are parallel to or in the plane of the recording layer, or perpendicular magnetic recording disks, wherein the magnetization directions are perpendicular to or out-of-the-plane of the recording layer. To produce the required magnetic isolation of the patterned data islands, the magnetic moment of the spaces between the islands must be destroyed or substantially reduced to render these spaces essentially nonmagnetic. In one type of patterned media, the data islands are elevated, spaced-apart pillars that extend above the disk substrate surface to define troughs or trenches on the substrate surface between the pillars. The magnetic recording layer material is then deposited over the entire surface of the substrate to cover both the ends of the pillars and the trenches. The trenches are recessed from the tops of the pillars so they are far enough from the read/write head to not adversely affect reading or writing.
In the proposed patterned disks, the data islands are equally spaced along single data tracks with the data tracks being equally spaced in the radial or cross-track direction. The read and write heads read and write the data islands on a single track so the data islands are typically sized to generally match the lateral or cross-track width of the heads. The data islands are spaced to define a bit aspect ratio (BAR), i.e., the ratio of the cross-track width to the along-the-track width required for a single bit, of near 1:1 because it is difficult to fabricate data islands with a BAR much greater than 1:1. However, it is difficult to fabricate heads with the proper performance for very narrow tracks with data islands having this low BAR. Also, if the single data tracks are too closely spaced, islands in tracks adjacent to the track being written may also be written by fringing fields from the write head, and the readback signal from a data track being read may receive interference from data recorded in adjacent tracks. To address these problems a patterned media disk drive has been proposed with heads that are two tracks wide. This allows the heads to be wider, which makes them easier to fabricate, and also allows the drive to read and write two tracks at a time, thereby doubling the data rate and bringing the performance closer to conventional disk drives. This type of patterned media disk drive is described in U.S. Pat. No. 6,937,421. However, regardless of the type of patterned media disk drive, i.e., whether the heads are a single-track wide or two tracks wide, there is no accommodation of the data island spacing and track spacing to maximize the areal data density.
What is needed is a patterned magnetic recording medium, and recording system that incorporates the medium, that results in improved reading and writing of the data islands as well as increased areal data density.